Several methods and approaches for fault location in high voltage power systems have been developed and tried. One approach has been to use voltage/current transducers located at terminals, between which the power lines to be monitored run.
One such system is disclosed in U.S. Pat. No. 5,455,776 where the transducers are connected to transducer blocks and a fault location estimation processor. The system uses positive or negative sequence networks.
Iterative calculations are used in U.S. Pat. No. 5,455,776 for determining the synchronization angle. In the disclosed method of U.S. Pat. No. 5,455,776, the unknown synchronization angle (δ) is to be calculated by an iterative Newton-Raphson method and after this, the fault distance can be determined. The Newton-Raphson approach utilized in the method, starts from the initial guess for the synchronization angle set at a certain pre-defined value (usually equal to zero). As a result of iterative computations the nearest mathematical solution (which is the closest to the assumed initial guess) is reached. This approach seems to be reasonable for a majority of applications, as the other solution for the synchronization angle (which is mathematically possible but rejected here) is usually far away from the assumed initial guess and outside of the reasonable range. However, for some heavy fault cases (large difference of the detected instants of a fault occurrence performed at both line ends) there is a risk that the rejected solution is regarded as a correct result, while the reached solution is false.